1. Field of the Invention
The embodiments disclosed herein relate to transistors and, more particularly, to a transistor structure (e.g., a bipolar junction transistor (BJT) structure or a heterojunction bipolar transistor (HBT) structure) with a collector region having a protected outer edge portion for reduced base-collector junction capacitance Cbc and to a method of forming the transistor structure.
2. Description of the Related Art
For transistors used in radio frequency (RF) applications (e.g., bipolar junction transistors (BJTs) and, particularly, high performance heterojunction bipolar transistors (HBTs)), it is desirable to have a relatively high transit frequency ƒT and a relatively high maximum oscillation frequency Fmax. Fmax is a function of ƒT and also of various parasitics, including parasitic resistances and parasitic capacitances. One such parasitic capacitance is base-collector junction capacitance Cbc. Reduction of this base-collector junction capacitance Cbc can result in a higher Fmax. Thus, it would be advantageous to provide a transistor structure, such as a bipolar junction transistor (BJT) structure or heterojunction bipolar transistor (HBT) structure, with reduced base-collector junction capacitance Cbc as well as a method for forming such a transistor structure.